Renal viability evaluated by the multiprobe assembly: A unique tool for the assessment of renal ischemic injury

Background: One of the major causes of transplanted organs' dysfunction is ischemia-reperfusion injury, where mitochondrial dysfunction is the primary contributor to cell damage. Mitochondrial NADH fluorescence reliably describes intracellular oxygen deficiency and mitochondrial function. Therefore, its monitoring at the tissue level, together with other physiological parameters, can serve to evaluate tissue vitality. Methods: The multiprobe assembly (MPA) enabled the assessment of renal blood flow (RBF) using laser Doppler flowmetry, mitochondrial NADH redox state using the fluorometric technique, and ionic homeostasis using specific mini-electrodes (K⁺ and H⁺). The MPA was utilized in two rat groups in which ischemia was induced for a period of 25-30 min (group 1) or for 60 min (group 2), and RBF and NADH were also monitored in a group of rats that underwent a complete kidney ischemia 24 h before the monitoring - a well-known model of acute renal failure. Results: During ischemia, the RBF was completely abolished, NADH and extracellular potassium levels increased, and extracellular pH decreased. Immediately after the reperfusion, full recovery was observed; however, in the rats undergoing 60-min ischemia followed by 24-hour reperfusion, the tissue hemodynamic and mitochondrial functions were significantly impaired. Conclusion: This study demonstrates the advantage of using the MPA for real-time evaluation of kidney physiological state, which may serve as a practical instrument for the evaluation of graft viability during transplantation procedures.